The present invention relates to an automatic transmission and particularly to a volume control device for a variable volume pump mounted to an automatic transmission. More particularly, the present invention relates to an improvement in mounting a volume control device.
Commonly, an automatic transmission comprises a combined structure of a transmission case with a converter housing, the transmission case accommodating therein a change speed gearing and various frictional elements which have a function to shift speed ratio by switching power delivery path, the converter housing accommodating therein a torque converter to be disposed between the change speed gearing and an engine. An oil pump which is adapted to supply actuating oil to the above mentioned frictional elements and the torque converter is arranged near the mating surface of the transmission case with the converter housing.
In the case of the above mentioned oil pump is a variable volume pump, a volume control device thereof may be constructed and arranged in such a manner as disclosed by Japanese Patent Application Provisional Publication No. 57-62986 or as illustrated in FIG. 2. That is, there is formed a cylinder bore c in a converter housing b to which a transmission case a is fixedly secured, a piston d is slidably fit in this cylinder bore c, and a push rod e has one end engaged with the piston d and an opposite end abuttingly engaged with a volume varying element (not shown).
With this volume control device, a control pressure is supplied to a pressure chamber f, urging the piston d and the piston rod e to move the volume varying element, and the volume of the pump can be controlled by this movement of the volume varying element.
However, since according to the volume control device constructed as above the cylinder bore c is formed in the converter housing b and the piston d is disposed in the cylinder bore, the axial length (horizontal length as viewed in FIG. 2) of the automatic transmission inevitably increases by an amount corresponding to a diameter of the cylinder portion having the bore c.